Ptjmp



June 28, 1927. 1,634,023

c. M. DAvxsoN PUMP Filed March l5. 1926 ,mman

l .ci

Patented .lune 28, 1927.

unirse STATES twat@ PATENT OFFQE.

OLARENCE MARION DAVISON, OF BALTIMORE, MARYLAND, ASSIGNOR TO POOLE ENGI- NEERING & MACHINE COMPANY, F BALTIMORE, MARYLAND, A CORFORATION OF MARYLAND.

PUMP.

Application led March 15, 1926. Serial No. 94,894.

This invent-ion relates to improvements in pumps, the primary object ot the invention being to devise a pump especially designed for use in circulating the refrigerating medium of refrigerating system from the cooling unit of said system, at which time said medium is in a gaseous state to the condenser and back again in liquid form to the cooling element,

A further object is to provide a pump of this character in which therewill be an effective oil seal for the gaseous refrigerating medium when the same is being pumped thereto.

A further object is to provide for the circulation of a sealing medium used in the pump in such fashionas to reduce the power required for operating the pump at a speed to obtain a given pressure. Expressed differently, the object is to permit the same pressure which has hereinbefore been obtained in prior devices to be obtained in the present instance with the use of approximately one third less power.

With these and other objects in viewthe present invention consists in certain novel details of construction and combinations and arrangements of parts, all as will be hereinafter more fully described and the novel features thereof particularly pointed out in the appended claims.

Y 1n the accompanying` drawings,

Figure 1 represents a side elevation, partly in elevation and partly in section of aY pump embodying the present improvements, the section being taken on line 1 1 of Fig. 6.

Fig. 2 is a similar View of the side opposite to that shownin Fig. 1.

Fig. 3 is a sectional view on the line 3 3 of F ig. 5, the gears being shown in elevation.

Fig. 4 is a sectional view on the line 4 4 of Fig. 3.

Fig. 5 is a sectional view on the line of Fig 8.

Fig. 6 is a sectional view on the line 6 6 of Fig. 3.

a portion only of said casing being shown in the present instance as it forms no part of the'improvements claimed herein. Casing 10 1s formed with an inwardly extending boss 11 against which abuts a bearing plate 12 and spaced from said bearing plate 12 is a second bearing plate 13, said bearing plates being held in their proper spaced relation by a segmental member 14 which partially houses the gears 15 that are located intermediate the two bearing plates. Both of said bearing plates and segmental housing 14 for the gears are supported from the boss by means of bolts 16 whose headed ends engage the exterior face of the bearing plates 13 and whose opposite threaded ends are received in threaded sockets in the pump casing 10. To facilitate alinement of the several members that are thus carried by the boss and bolts they are preferably snpported by sleeves 17 through which the l-olts 16 extend, said bolts primarily functioning as clamping means. y

- The shaft 18 of one gear 15 is journaled in bearings in the two end plates 12, 13 while the other gear has a shaft 19 elongated so as to extend through a packing gland 20 in the casing 10, its projecting end located cxi'eriorly of the casing being connected to any suitable driving means for rotating the gears. Vith the construction outlined it will be seen that the gear teeth are housed by the end plates and the segmental housing 14 during a portion only of their rotation. Extending through the housing 10 and end plate 12 is a gas duct 21 through Vwhich gas may be introduced into the spaces between the adjacent gear teeth at a time just after the tooth of one gear begins to withdraw from the root of the cooperating pair of teeth on the other gear and also at the time the teeth between which the gas is thus introduced are passing into Contact with the enclosing wall of the segmental housing member 14. The gas supplied to the duct 21 is at least under atmospheric pressure and as one tooth of one gear begins to withdraw from between the two teeth of the other gear it is apparent that there will be a tendency on the part of the gas to. rush or be sucked into the evacuated space between said two teeth. The teeth of gears 15 are spirally cut and said gears are so mounted that the teeth thereof engage each other first at the intake end or the end abutting against bearing plate 12 and, as they are rotated past the inlet port FE1, and begin to disengae'e there will be a space hetween the root or the tooth oi one gear anc the corresponding crown of the other. il u-`A ther, owing to the tact that the gears are spirally cut such space will gradually enl large as the gears rotate int. housing and consequenlinta-ire port will comple In this way the space het two adjacent teeth et l tially lilled with the. other medium.

To build up a pre,Cm ou the gas thus introduced into the c ies between the teeth of the gears a coniiiedinr usually in the l'orinot oil is introduced under pressure into each of said cavities zitter the e s has been introduced into the the teeth pass beyond the evitrenii i segmental housing ln the co lustrated this compi ig med i duced at a plurality oi po i; of the gears, the consti.' l rc'terred consisting in forming ducts 22 in t iental housing 14 and enc hearing iat 12, the compressing med ,in :tloi "fn said ducts into the z through passages asillustrated in Figs. 1, 6 and .7. rlhe coi 'essing mediun'iis supplied through a litting 24 in the casing 10 to a groove 25 in the end bearir plate 12, and said groove communicates with both the longitudinally xtending ducts 22 as shown in Figs. l ',lihe medium supplied to this groove 35 `will'be termed the primary supply because in sonic cases there is an auxiliary snpol ne( in to the gear teeth. l'lhere si up is used it ma"7 talle the i 1 u duct extensing through the segmc al housing lfiland end plate 12, the coi rli in being delivered to said duct throilgi i ng 2st" and flowing irom said duct to the teeth through the passages 23?.

As the gear teeth i u bef/*on ties oi the segmen' i l therefrom under jf under such pressure, in until there is up snmcient within said Vtorce the condenser o'lthe ret r: vs portion oit the appar 'aus y companying drawings bein; i more or less surrounded by the r l ating gas, under pressure, wit in the pump chamber, it is apparent that there is always. a tendency o'l such surroundi is to iind its way back into the ce" ier l i wenn the teeth, and as the etliciency et tT e apparatus depends upon the quantity o s that can be taken into said cavities thro `r`.h the n( 1inal gas supply duct Q1, it important that no from within the chamber should be adtl ie extremilows l 1 Di casing to mitted to said cavities to partially fill the latter and thereby reduce the volume of gas that can be taken through the normal supply-duct 21. For this reason the compressing mediuni is usually in the for-1n -of oil in order that such oil may tor-m a iil'm on the gears and act as a sealing agent to prevent leakage ol' gas into and out ot the pockets formed by the gear teeth.

The oil thus introduced between the'teeth -for purposes ot con'ipressing the gas therein and tor torniing a liquid seal as `inst described'must, of necessity, be displaced from the teeth as said teeth come into complete engagement with each other at the end oi the gears opposite the inlet duct 21. In some of the devices ot the prior art this -displacement of oil l'rom between the teeth has been taken care of by having a comparatively loose lit between the ends ol' the gears and the bearing plate 13, but in such Adevices this looseness ot lit between such parts has been found to lower the ethciency of the pump because the space between the ends oli' the gears and the bearing plate 13 permits gas within the chamber to enter and partially .till the pockets formed by those teeth whose crowns are in engagement with the segmental housing 14. In the structure contemplated by the present invention this cultyot removing the oil iron-i the teeth is not only eliminated but, in addition, the lparts are so constructed as to have a close lit between the ends of the gears and bearing plate 13. For facilitating the escape ol" oil trom between the teeth as they fully intermesh at their ends adjacent plate 13 said plate is termed with a relief groove 2G in registry with the point at which the said ends of the gear teeth fully interniesh. in the absence of such a relief groove 26 or ot a loose lit between the parts it will be realized that the o-il cannot escape and 'the gears would be locked against further rotation, y'or to such an extent as to require excessive vpower for driving them. ln so 'far as lescape oit' the oil between the teeth is concerned the relief groove 26 need .only -be in registry with the point at which the teeth tnlly intermesh, but for other reasons it is preferred that said groove be ot Isuch dimensions as to extend to a point where the teeth after :having fully intermeshed have also begun t'o separate. l/Jith the relief groove of this character the initial opening oi. the teeth will permit a very small .quantity of `oil to lreenter them so that they are provided with loo the relief groove and receives a lilm of oil; and then the opposite end of that tooth passes the inlet duct 21 for the admission of gas between it and the next succeeding tooth.

- This provision of the relief groove 26 reduces the power necessary to drive the pump and to further reduce the quantity of power necessary the relief groove is preferably eX- tended so as to intersect the bearings of the shafts 18, 19 in the plate 13 and said bearings are formed with ducts 27 which permit the bearings to be thoroughly lubricated, it being understood that only a minor portion of the oil reenters the teeth from groove 26 while the greater portion thereof is caused to flow through the ducts 27 to the exterior of plate 13 whereupon it will drop and accumulate in the bottom of the pump casing chamber.

As has been stated it is desirable to have a neat fit between the ends of the gears and the adjacent bearing plates 12, 13. To secure this result the end faces of the gears are cut away around their shafts as at 28 leaving a comparatively narrow strip of metal between said cut away portions and the roots of the. teeth and consequently reducing the wearing surface on the gears. Likewise, the end plates are cut away as at 29 immediately around the bearings for the gear shafts. The comparatively restricted wearing surface between the gears and bearing plates is advantageous, and as a further advantage the depressions formed by the cut away portions in the ends of the gears permit those narrow wearing surfaces to be dressed olf very accurately7 much more so than would be the case if those wearing surfaces extended radially inward to the shafts of the gears. This is true because if those surfaces extended .entirely to the shafts it would be difficult to operate on the end face close to the shafts with the dressing tool.

By thus having narrow accurately finished en'd faces on the gears an exceedingly line lit can be had between such gears and the end plates, but this closeness of lit is not, however, relied upon entirelyfor preventing gas within the pump chamber gaining access to the points formed by the gear teeth. in addition the joints at these points are adapted to be provided with a liquid seal. it will be apparent that oil from relief groove 26 will find its way into depressions in rend plate 13 and the adjacent ends of the gears thus sealing the joint between these ends of the gears and said end plate. For supplying oil to the cavities in the opposite ends of the gears and in the bearing plate 12 passages 30 are formed in said bearing plate 12 between the oil supply duct 24 and the bearings for the gear shafts and said bearings have a small duct 31 extending longitudinally thereof to permit the oil to How into the cavities and the joint between bearing plate 12 and the adjacent ends of the gears.

As a summary, it might be stated that the introduction of oil into the spaces between the gear teeth by means of the elongated oil ducts 22; the provision of the relief groove 26 for facilitating the discharge of. the oil from between the teeth as they intermesh at their ends adjacent bearing plate 13 and the provision of the oil ducts 27 in the shaft bearings for lubricating those bearings; the location of relief groove 26 so as to introduce a small quantity of oil into the gear teeth as their ends adjacent bearing plate 13 begin to sepa-rate and before their opposite` ends come into registry with gas inlet duct 21; and the provision of the comparatively narro v wearing surfaces at the ends of the gears combined with the oil receiving depressions in said ends and the adjacent faces of the bearing plates; all tend to produce a pump which is not only very efficient in operation but which may be operated at a much lower cost. In actual tests compressors equipped with these new features have been capable of obtaining pressures at least 50% in excess of those obtainable with other types of machines, this difference in pressure indicating not only an increase in efficiency but at least 331/3% reduction of the power required to drive the pump. That is believed to be due primarily to the provision of the relief groove in the bearing plate 13 and the thorough liquid seal which is obtained in the present pump and, also, the thorough lubrication of the rotating parts. Another advantage is the particular way in which the oil is introduced between the gear teeth. That is, the use of the oil supply passages 22, 22a, insures the oil being equally distributed along the entire length of the teeth regardless of that length. Not only is a minimum amount of oil required with this arrangement but there is a resultant reduction in the power required to drive the pump. If the oil should be introduced through a port at the ends of the teeth, the same as the gas, itr-emains in globular form and produces water hammer effect when impacting against the bearing plate at opposite end. This has been found to be true in actual practice and in an effort to secure a more thorough distribution of the oil and thereby eliminate the noise made by the water hammer effect, a comparatively large quantity o-f oil has been introduced at the ends of the spaces in the comparatively short period of time such spaces are in registry with the oil opening but, such efforts have only resulted in an increase in the power required to drive the pump without securing` the desired results which, it seems, can be secured only by introducing the oil at points along the teeth.

and sealing said fluid therein during a portion of the rotation of each pair of interineshing teeth, one face of each pair of abutting faces of the gears and plates having its central portion cut away to reduce the wearing surface between the gears and plates an-d provide a cavity for the reception of a sealing and lubricating medium.

l0. In a pump, the combination with the pump chamber casing, of' intermeshing spirally cut gears` means for introducing the pumped fluid into spaces between intermeshing teeth at one end of' the gears, and means for introducing` a Sealing medium into the space between adjacent teeth of' the gears at a plurality ol' points longitudinally of the gears.

ll. In a pump, the combination with the pump chamber casing, of inter-meshing spirally cut gears, means for introducing the pumped fluid into spaces between inter-l meshing teeth at one end of the gears, and means for introducing` a sealing medium into the space between adjacent teeth of the gears at points located adjacent both ends of' the gears.

l2. In a pump, the combination with the pump chamber casing, of intermeshing spirally cut gears, a bearing plate at each cud of the gears, a segmental housino intermediate said plates partially enclosing the gears, means for introducing the pumped fluid into the spaces between intermeshing teeth at one end of the gears, and means for introducing a sealing liquid into the spaces between said teeth, said last mentioned means comprising a duct in said segmental housing extending longitudinally of the gears and communicating with the spaces between the gear teeth at a plurality of points longitudinally of said gears.

CLARENCE MARION DAVISON. 

